The present invention concerns a constant air flow rate valve where, in a flow passage confined by a passage section, has been disposed a throttling member presenting a throttling part which changes shape.
A constant air flow rate valve of this type has been disclosed e.g. in the EP Pat. No. 0027068. Constant air flow rate valves of prior art have an elastic throttling member which has been placed in the interior space of the air passage. When the differential pressure acting across the throttling member increases, the throttling member changes shape so that the flow aperture is reduced. The higher the differential pressure becomes, the smaller becomes the flow aperture similarly, decrease of the differential pressure causes the flow aperture to grow larger. In this way the air flow passing through the constant air flow rate valve is kept approximately constant.